Every month, as the Moon circles the Earth is its elongated orbit, its distance from the Earth varies. At perigee (its closest approach to Earth), it is 14 percent closer than at apogee, and when the Moon is simultaneously at perigee and in line with the sun, as happens at full moon and new moon, it produces the greatest tides. These tidal differences are measured in feet not fractions of an inch, and the unusually close approach by the Moon on Jan. 4, 1912, may have caused abnormally high tides. The Texas State research team investigated how pronounced this effect may have been.

What they found was that a once-in-many-lifetimes event occurred on Jan. 4 of 1912. The Moon and Sun had lined up in such a way their gravitational pulls enhanced each other, an effect known as a “spring tide.” The Moon’s perigee proved to be its closest in 1,400 years, and came within six minutes of a full moon, maximizing the Moon’s tide-raising forces on Earth’s oceans. On top of that, the Earth’s perihelion—closest approach to the sun—happened just the day before. The odds of all these variables lining up in just the way they did were astronomical.